Desizing textiles



Patented Sept. 12, 1939 UNITED STATES PATENT orrlca No Drawing. Application February 24, 1937, Serial No. 127,569. In Austria March 23, 1936 15 Claims.

This invention relates to the desizing of sized textiles of all kinds, particularly to the removing of starchy material from sized textiles, and to products suited for this purpose.

As is well known, the fibres of sized textiles require a cleansing pre-treatment before being subjected to further processes such as. bleaching, dyeing, printing, and the like, since in addition to natural fats and waxes they also contain, as a result of the spinning process, oily or greasy contaminating matter, and especially sizing agents,

as a rule starch and sometimes (in addition to such starch) also dextrin, glue, vegetablegum and vegetable mucilage, or the like. Such foreign bodies must be removed as completely as possible before treatment with bleaching agents or dyestuffs, in order to give the baths access to the textile fibres.

An object of the invention is to remove the size of textiles in a simple and eflicient manner.

Another object of the invention is to prepare the sized materials for further improving processes, e. g. .for bleaching and dyeing in a relatively short space of time.

A further object is to impart to the textiles treated a high absorbing power ensuring in subsequent bleaching and/or dyeing processes a uniform action of the baths used and avoiding the occurrence of spots and irregularities in a better way than hitherto possible.

Further objects will appear as the description proceeds.

The present invention is based on the recognition that the salts of persulphuric acid (HzSzOa) have an entirely specific and particularly intensive effect in removing the size of textiles, which is far superior to that of other oxygen-yielding compounds. The method according to the invention consists in contacting the sized textile with a watery solution of salts of persulphuric acid. In general a relatively small amount of persulphate is used. According to my experience in'this field of the art a concentration of 0.2 gramme to 2 grammes of the said salts per litre of the solution is sufficient to obtain regularly the desired effect. v

According to a particular mode of carrying out the invention there are added to the solution in addition to persulphates other compounds containing a group of the general formula R-O-O-R. This group is characteristic of hydrogen peroxide, its derivatives, and compounds containing hydrogen peroxide in place of water of crystallization or bound in any form. Thus, to these compounds for example there belong in general per-salts, e. g. percarbonates, perphosphates or perborates, further peroxides such as for example sodium peroxide or calcium peroxide, and hydrogen peroxide. If desired, a plurality of these additional substances may be introduced into the solution containing persulphate. What is essential, however, is that persulphates be always present in the solution for removing the size, since the action of persulphate 10 is of decisive importance for the complete and rapid removal of the size from the fibres, while the addition of other per-compounds has the effect, mainly, of bringing about favorable secondary results. Such additions have the efl'ect, more particularly, of preventing any discoloration that might otherwise occur, and also at the same time allow of a particularly good pre-bleaching of the fibres to be eflected.

Since persulphates are eflicient in removing the 20 size, no matter whether the treating bath be alkaline, or neutral or acid, the method according to the invention is in principle applicable to all vegetable, animal, and artificial textile materials. Thus this method may be employed not only for the treatment oi cotton and other cellulose fibres, such as linen, hemp, ramie, and jute, but also for the cleansing and desizing of animal fibres, such as wool and silk. The method is likewise applicable for the cleansing and removal of 30 size from every kind of artificial fibres, particularly rayon and mixed materials. The method according to the invention aflords the possibility of adjusting the bath so as to be alkaline, neutral, or acid, as may be desirable forzany particular fibre, and also of combining the removal of the size with other, conventional, treatments which must be carried out in a bath having a definite concentration 01 H and OH-ions, respectively.

(A) The employment of persulphate containing baths of strong alkalinity is suitable more particularly for the removal or size from cotton goods (white goods). For this purpose there are employed caustic alkaline baths the alkali content of which corresponds to more than 2 5 grammes of NaOH, for example 3.5 g. up to 5 g., and even to 10 g. and more, of NaOH per litre of the bath. Instead of NaOH, of course, correspondlng quantities of KOH may be used for producing the desired strong alkalinity. The described treatment may be carried out without diificulty at temperatures 01' 50 to 60 C., and even at a lower temperature. If importance be attached, however, to eflecting rapid removal of size the work is carried out at temperatures in excess of C. or at boiling temperature, in which case, under favorable circumstances, it is sufficient to convey the goods once through the bath for the purpose of removing the size from the same.

A point of particular significance is that when carrying out the removal of size by the method according to the invention boiling (bucking) baths employed subsequently thereto remain far cleaner than with the method oi working hitherto adopted, since, apart from the size, a large part of the other impurities is also removed before bucking.

The removal of size with caustic alkaline baths is also applicable, with advantage, to the treatment of colored, striped or bordered materials provided in addition to persulphate there be added to the bath slight quantities of H20: or its derivatives, in which case not even the treatment of naphthol dyed material is impossible. The additional bleaching effect achieved by the described pre-treatment may even go so far that a single subsequent oxygen bath of a known type suffices to complete the bleaching.

For the treatment according to the present invention it is also possible to employ used boiling baths or oxygen bleaching baths if the treatment concerned is to be effected with an alkaline bath. If used bleaching baths are employed, besides persulphate there are added agents which bring about a suitable increase of the alkalinity of the baths. In the case of the strongly alkaline bucking baths it is as a rule sufllcient to add persulphate in the necessary concentration.

Freshly prepared persulphate-containing baths for the removal of size, which contain caustic alkali, may also perfectly well be employed as boiling baths, in which case the removal of size and bucking are carried out consecutively in one and the same bath. This combination of the removal of size and bucking has proved particularly suitable for the treatment of cotton goods.

(B) In using persulphate-containing baths for the removal of size, more particularly when the removal of size is carried out at temperatures of 80 C. or higher, good results can be obtained even when the bath has an OH-ion concentration which is lower than that in a bath the alkalinity of which corresponds to an NaOH content of 2 grammes per litre. It is thus for example possible, with the aid of persulphate-containing baths having an alkali content of l gramme of NaOH per litre or for'example of 2 grammes to 3 grammes of sodium carbonate or ammonia or ammonium carbonate per litre, to obtain excellent desizing results, more particularly at temperatures of 80C. or higher. However, it is not only possible to carry out the removal of size with weakly alkaline baths but the baths may even be neutral or weakly acid. Treatment with weakly alkaline, neutral, or acid baths is primarily advisable for the treatment of fibres sensitive to alkali, such as more particularly animal fibres or mixed products containing animal fibres, but is also suitable for cotton and other cellulose fibres and particularly advantageous for colored, striped or bordered materials and nappy materials, such as velvets, flannels, and the like. In the treatment of cotton and the like it is usual to follow up the described removal of size with a bucking. If weakly alkaline baths are to be employed either suitably small quantities of caustic alkali may be added to the bath, or, better still, the bath may be rendered alkaline with the aid of compounds causing an alkaline reaction other than caustic alkalies. Examples of such compounds are preferably carbonates, secondary and tertiary phosphates, pyrophosphates, metaphosphates, borates, and the like. These salts causing a weakly alkaline reaction may also be employed as additions to baths containing suitably slight quantities of caustic alkali. Even weakly alkaline baths and baths to which there have been added, in addition to persulphiate, only such slight quantities 01' compounds causing an alkaline reaction that the alkali present is just sufficient to neutralize the sulphuric acid formed by decomposition of the persulphate, so that the bath becomes neutral in the course of the treatment, suflice for bringing about the effect aimed at. The speed at which the removal of size takes place depends in this case primarily on the temperature employed, and increases with the temperature. The same applies for the employment of baths which assume acid reaction in the cours of the treatment, whether the baths are employed without the additional introduction of compounds causing an alkaline reaction, or whether the added quantity of alkali is so limited that the alkali does not suflice to completely neutralise the sulphuric acid formed. It is thus possible to carry out the cleansing and removal of size even in acid baths. Such baths may also be brought to the desired degree of acidity by the direct addition of compounds causing an acid reaction which are added before commencement of the treatment or during the treatment.

The removal of size in accordance with the present invention can also be combined with other, conventional, treatments. Thus, for example, the removal oi size may be combined with a bleaching. Further combinations are possible with various pre-treatment baths, such as for example in the treatment of colored, striped or bordered materials with the boiling or scalding bath. Persulphate may be added to a bath of this nature, with the result that the boiling or scalding and removing of size are comprised in one process step, and the dyes at the same time protected from becoming vatted. In view of the many special processes known to the textile art there are, of course, numerous other possibilities of combining with some other treatment the removal of size with the aid of persulphate.

As far as piece goods are concerned, the removal of size may be carried out in any impregnating or washing machine. Since the described baths are non-sensitive to a great extent to catalysts the rollers of the apparatus employed may even consist of iron or copper. The treatment may also be carried out by steeping the goods in vats or circulation apparatus, kettles, jigs, in a machine for impregnating material in unfolded condition (open width), on the reel or on the clapot, or the like, the goods being allowed to rest either under the bath or after squeezing out. This mode of treatment is adopted more particularly in the case of yarns, tricot, and other kinds of goods which are not as a rule passed through impregnating machines.

It has proved advisable to wet the goods, and especially singed goods (above all' closely woven piece goods), before the removal of size, with hot water. For this purpose the material is passed,

, after singeing, continuously, and preferably unfolded, (open width), through hot water. This treatment very considerably shortens the process of removing the size, since the bath proper for the removal of size is then able to penetrate rapidly and uniformly.

In this connection it is practically immaterial whether the goods are allowed to rest for a considerable length of time after the treatment with hot water or are further treated at once, but care is preferably taken to ensure that the goods do not dry up again before further treatment. Instead of the .preliminary wetting with hot water it is also possible to use hot baths containing wetting agents. All conventional wetting agents may be employed for this "purpose. The wetting agents may'also be added to the treating bath itself. The products from which the size has been removed in accordance with the invention are then further improved in a known manner, for example bleached. dyed, printed, or the like.

Examples (1) 1000 kgs. of cotton piece goods, destined to serve for the manufacturing of whites, are treated in an impregnating machine with a bath containing, for every 1000 litres of bath, 10 litres of caustic soda solution of B. and 2 kgs. of sodium persulphate. The temperature of the .bath is about 80 to 90 C. The liquid absorption of the goods coming from singeing amounts to some dered materials made from American cotton are impregnated on a clapot with a bath containing, for every 1000 litres of bath, 7 litres of caustic soda solution'of 40 B., 1 kg. of potassium persulphate, and kg. of hydrogen peroxide of 30% strength. The bath has a temperature of C. The material is allowed to rest over night in a wooden tub, the surplus used bath being used to cover the material. After this treatment the material is run over a washing machine into a circulation apparatus and there bleached to its final condition in a known manner with an oxygen bath. r

(3) 500 kgs. of piece cotton goods or cotton hosiery are brought, for the purpose of removing the size and bucking, together in a boiling vessel with a bath containing, in 1500 litres, 10 kgs. of caustic soda and 1 kg. of potassium persulphate (if desired with additions of 0.5 kg. of H202 or (78.02) The temperature of the running in bath is between 50 and C., and is raised, during circulation, within about an hour, to 100 C. During this heating up period the removal of s'me takes place completely and uniformly. .The boiler is then tightly closed as usual, after which the boiling under pressure is effected. Spotless material of which the size is completely removed is obtained.

(4) 1700 kgs. of calico is wetted with hot water after singeing, and run over a washing machine into the bucking kier. There then follows the treatment with a bath containing 1 gramme of potassium persulphate and 1 gramme of NaOH per litre, for two hours, at to C. The bath is run off with the impurities, after which normal bucking is effected. After the treatment with the persulphate containing bath the calico is completely free from size.

v (5) 100 kgs. of woolen fabric is treated on the reel vat for two hours in an initially approximately neutral bath containing 1 gramme of sodium persulphate per litre, at 90 C., the bath becoming graduallyacid in the course of the treatment. There is obtained clean material perfectly free from size which bleaches very well.

(6) 150 kgs. of cotton fabric is impregnated with a hot (90 C.) bath containing 1 gramme o1 persulphate per-'litre-if desired. with an addition of 1 gramme of soda per litre-and allowed to rest over night. The subsequent alkaline boiliriizg or alkaline bleaching yields material free. from s e.

('1) kgs. of corduroy is boiled for three hours on a reel vat in a bath containing 1 gramme of potassium persulphate and 0.5 gramme of potash-and if desired 0.3 gramme of metaphosphate, per litre. The resulting removal of size is complete; inaddition, the treated material is beautifully soft and behaves excellent on brushing. Instead of the above mentioned bath there may also be employed a bath containing 0.65 gramme of potassium persulphate and 0.35 gramme of soda per litre, the bath becoming neutral in the course of the treatment.

(8) 60 kgs. of stout woollen fabric is bleached on a jig in a bath containing 8 litres of hydrogen peroxide (40%) and 0.5 kg. 'of sodium pyrophosphate in 250 litres of bath. In order to enable the size 'to be removed there is further added to the bath 200 grammes of persulphate (likewise to 250 litres of bath). The temperature at which the treatmentis'carried out is 35 C.

In the following claims I use the term sized textile to mean textile yarns and textile fabrics carrying sizing agents consisting of or containing polymeric carbohydrates selected from the group consisting of dextrin, vegetable gum, and vegetable mucilage, and particularly starch.

I claim:

1. ma process of desizing'textilesthe step of contacting a textile material which carries a polymeric carbohydrate as an essential sizing agent, with a watery solution of a persulphate, while at above ordinary room temperature.

2. In a process of desizing textiles carrying a size which includes starch, the step of contacting a sized textile at a temperature between 50 and C., with an amount of persulphate which is only a minor fraction of the amount of the size present, the persulphate being in watery solution.

3. In a process of desizing textiles sized with a polymeric carbohydrate, the steps of treating a sized'textile with'a hot aqueous solution having an alkaline reaction and thereafter bringing the said pre-treated textile into contact with a watery solution containing a salt of persulphuric acid and allowing the salt to act, at an elevated temperature, upon the pretreated sized textile.

4. In a process of desizing a textile sized with starchy material, the steps of introducing such a sized textile into an alkaline reacting aqueous bath containing a salt of persulphuric acid and subjecting said textile to the action of the said bath at a temperature between 50 C. and 90 C. until the size has been substantially dissolved and then carrying out a bucking in the same bath.

5. In a process of desizing textiles carrying a sizing which contains starch, the step of contacting such sized textile, at an elevated temperature, with a watery solution containing between 0.2 and 2 grams of a persulphate per litre.

6. In a process of desizing textiles carrying a sizing which contains a polymeric carbohydrate of the type n(CoH1oOs), the step of contacting such a sized textile, at an elevated temperature, with a waterysolution comprising a salt of persulphuric acid and in addition thereto another compound selected from the group consistlng or hydrogen peroxide and per-compounds yielding, on decomposition in aqueous solutions, hydrogen peroxide as an intermediate product.

'7. In a process of desizing textiles the step 01.

'contacting a textile sized with a size contain-.

ing starch as its largest component, at an elevated temperature, with a watery solution containing per litre 0.2 gram to 2 grams of a salt 01' persulphuric acid and in addition thereto another compound selected from the group consisting of hydrogen peroxide and percompounds yielding, on decomposition in aqueous solutions, hydrogen peroxide as an intermediate product.

8. In a process of desizing textiles the step of contacting a textile material sized with a starchy material, at a temperature above normal room temperature, with an alkaline solution of a salt of persulphuric acid.

9. In a process 01' desizing textiles the step of treating a starch-sized textile article, at above normal room temperature, with an alkaline solution containing a salt of persulphuric acid, the

said alkaline solution containing in addition to the said salt of persulphuric acid, another compound selected from the group consisting of hydrogen peroxide and percompounds yielding, on decomposition in aqueous solutions, hydrogen peroxide as an intermediate product.

10. In a process of desizing textiles the step of passing a starch-sized textile, by continuous movement, through a hot wetting bath and thereupon through a desizing bath containing a salt of persulphuric acid, at such a rate of movement that on leaving the desizing bath any size still present on the thus treated textile is so modified as to be soluble.

11. In a process desizing textiles the step or treating sized textile material carrying a size which contains starch as a large component,

while at above normal room temperature, with a watery solution oi a salt of persulphuric acid, and adjusting the initial OH-ion concentration 01' said solution so as to be below an OH-ion concentration which corresponds to a NaOH-content 01 2 grammes per litre.

12. In a process or desizing textiles comprising the step of treating a textile carrying a sizing of a starchy material while at above room temperature, with a watery solution ot a salt of persulphuric acid, the said solution containing an amount or a compound having basic properties, which is only about suillcient to neutralize sulphuric acid formed by decomposition of the persulphate during the treatment.

13. In a process 01' desizing textiles the step of treating textile material sized with a material which includes a polymeric carbohydrate of the type n(CsH1oO6) -as' a major component, while at an elevated temperature, with a watery solution of a salt of persulphuric acid, and adding to said solution a compound having basic properties in such a limited amount that the bath assumes an acid reaction during the treatment as a consequence of decomposition oi. the persulphate taking place during said treatment.

14. In a process 01' desizing textiles the step of treating starch-sized textiles at an elevated temperature with a watery solution 01a salt of persulphuric acid, the said solution also containing other acid material in addition to the acid material produced from said salt of persulphuric acid.

15. In a process of desizing cellulosic textiles carrying a size which contains starch, which comprises the step or treating the said sized textile at an elevated temperature with a watery solution of a salt of persulphuric acid, the said solution containing alkali in an amount corresponding to more than 2 grammes of NaOH per litre.

JOSEF MULLER. 

